Dev Tools — HelpyTools

JSON Formatter

Format, minify, and validate JSON with syntax highlighting and error detection.

Input

Regex Tester

Test regular expressions with real-time pattern matching, capture groups, and a quick reference guide.

/ /

Test string

Matches

Enter a pattern and test string to see matches.

Character classes

.Any character except newline

\wWord character [a-zA-Z0-9_]

\WNon-word character

\dDigit [0-9]

\DNon-digit

\sWhitespace (space, tab, newline…)

\SNon-whitespace

\tTab

\nNewline

\rCarriage return

[abc]Character class — any of a, b or c

[^abc]Negated class — anything except a, b, c

[a-z]Range — any lowercase letter

[a-zA-Z]Range — any letter (case-insensitive)

Anchors & boundaries

^Start of string (or line with m flag)

$End of string (or line with m flag)

\bWord boundary

\BNon-word boundary

\AStart of string (no multiline)

\ZEnd of string (no multiline)

Quantifiers

*0 or more (greedy)

+1 or more (greedy)

?0 or 1 — makes preceding token optional

{n}Exactly n times

{n,}At least n times

{n,m}Between n and m times

*?0 or more (lazy — as few as possible)

+?1 or more (lazy)

??0 or 1 (lazy)

Groups & alternation

(abc)Capturing group — stores match in $1, $2…

(?:abc)Non-capturing group — groups without storing

(?<name>abc)Named capturing group — accessible as $<name>

a|bAlternation — matches a or b

\1Backreference — refers to group 1's match

\k<name>Named backreference

Lookaheads & lookbehinds

(?=abc)Positive lookahead — followed by abc

(?!abc)Negative lookahead — not followed by abc

(?<=abc)Positive lookbehind — preceded by abc

(?<!abc)Negative lookbehind — not preceded by abc

Flags

gGlobal — find all matches, not just the first

iCase-insensitive — A matches a

mMultiline — ^ and $ match line boundaries

sDotall — . matches newlines too

uUnicode — enables full Unicode matching

ySticky — match only at current position

Examples — click to load

/[\w.+-]+@[\w-]+\.[a-zA-Z]{2,}/gi Email address

Matches standard email addresses. The first part allows word chars, dots, + and -. After @, matches a domain and a 2+ char TLD.

/https?:\/\/(?:www\.)?[-\w]+(?:\.\w+)+(?:\/[-\w%@+.~#?&/=]*)? /gi URL

https? makes the s optional. (?:www\.)? is a non-capturing optional group. The path segment uses [-\w%@+.~#?&/=]* to cover query strings.

/^(?:\+?(\d{1,3})[-.\s]?)?…/gm Phone number (international)

Uses ^/$ anchors with the m flag to match one per line. \+? makes the country code prefix optional. Groups capture each segment individually.

/^#(?:[0-9a-fA-F]{3}){1,2}$|^#[0-9a-fA-F]{8}$/gm Hex colour

Alternation (|) handles 3-digit, 6-digit and 8-digit (with alpha) hex colours. {1,2} on the group allows either 3 or 6 hex chars after #.

/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[!@#$%^&*]).{8,}$/gm Password strength

Four lookaheads enforce rules independently: at least one lowercase, one uppercase, one digit, one special char. .{8,} enforces minimum 8 characters.

/^(?:(?:25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}…/gm IPv4 address

Each octet matches one of three alternatives: 25[0-5] (250–255), 2[0-4]\d (200–249), or [01]?\d\d? (0–199). The group repeats {3} times for the first three octets.

/(\b\w+\b)(?:\s+\1\b)+/gi Duplicate words

Uses a backreference \1 to detect the same word repeated. Group 1 captures a word, then \1 insists the next word is identical. The i flag ignores case.

/^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$/gm ISO date (YYYY-MM-DD)

Months use alternation to reject 00 and 13+. Days similarly handle the ranges 01–09, 10–29, and 30–31. Can't validate Feb 30th — that needs code.

Base64 Encoder/Decoder

Encode and decode Base64 strings with instant bidirectional conversion.

Plain Text

Base64 Encoded

JWT (JSON Web Token)

Decode, verify signatures, and generate JWT tokens with full payload inspection.

JWT Token

JWT Token

Algorithm

Secret (HMAC)

Header (auto-generated)

{"alg":"HS256","typ":"JWT"}

Payload

{"sub":"1234567890","name":"John Doe","iat":1516239022}

Secret (HMAC-SHA256)

Hash Generator

Generate MD5, SHA-1, SHA-256, and SHA-512 hashes from any input text.

Input text

MD5 —

SHA-1 —

SHA-256 —

SHA-512 —

Markdown Previewer

Write Markdown and preview HTML output in real-time with syntax reference guide.

Markdown

Preview

JS/CSS Minifier

Minify or beautify JavaScript and CSS code with compression and formatting options.

Operation

Remove comments Mangle names (JS only)

📂 Load file

package.json Analyser

Analyse dependencies and check Node.js version compatibility for your project.

📂 Load package.json or paste below

Test against Node.js versions: